Laravel 8 Eloquent 多对多插入数据透视表不起作用

Question

我正在尝试将数据插入到 Advertisement 和 AdvertisementCategory 之间的数据透视表中。首先，是的，就我而言，一个广告可以有很多类别。 顺便说一句：

我所有的模型都继承自我的 DatabaseObject 类。

<?php

namespace App\Models;

use Illuminate\Database\Eloquent\Model;

class DatabaseObject extends Model
{
    /**
     * Disables the
     * created_at and updated_at column creation
     * @var bool
     */
    public $timestamps = false;
}

这是我的广告模型：

<?php

namespace App\Models\Advertisement;

use App\Models\DatabaseObject;
use Illuminate\Database\Eloquent\Factories\HasFactory;
use Illuminate\Database\Eloquent\Relations\BelongsToMany;

/**
 * Basic Advertisement
 */
class Advertisement extends DatabaseObject
{
    use HasFactory;

    /**
     * Custom table name
     * @var string
     */
    protected $table = 'advertisement';

    public $fillable = ['name', 'description', 'sellingType', 'advertisementType', 'sellingPrice'];

    /**
     * A Advertisement has one AdvertisementCategory
     * @return BelongsToMany
     */
    public function advertisementCategories(): BelongsToMany
    {
        return $this->belongsToMany(AdvertisementCategory::class
            , 'advertisement2advCategory'
            , 'advertisementCategory_id'
            , 'advertisement_id');
    }
}

这是我的 AdvertisementCategory 模型：

<?php

namespace App\Models\Advertisement;

use App\Models\DatabaseObject;
use Illuminate\Database\Eloquent\Relations\BelongsToMany;

class AdvertisementCategory extends DatabaseObject
{
    /**
     * Custom table name
     * @var string
     */
    protected $table = 'advertisementCategory';

    /**
     * A AdvertisementCategory can have many advertisements
     * @return BelongsToMany
     */
    public function advertisements(): BelongsToMany
    {
        return $this->belongsToMany(Advertisement::class
            , 'advertisement2advCategory'
            ,'advertisement_id'
            ,'advertisementCategory_id');
    }
}

这是我的数据透视表对象：

<?php

namespace App\Models\Advertisement;

use Illuminate\Database\Eloquent\Relations\Pivot;

class Advertisement2AdvertisementCategory extends Pivot
{
    /**
     * Custom name for the table
     * @var string
     */
    protected $table = 'advertisement2advCategory';
}

这是迁移创建：

        Schema::create('advertisement2advCategory', function (Blueprint $table) {
            $table->id();
            $table->foreignId('advertisement_id');
            $table->foreign('advertisement_id')
                ->references('id')
                ->on('advertisement')
                ->onDelete('cascade');
            $table->foreignId('advertisementCategory_id');
            $table->foreign('advertisementCategory_id')
                ->references('id')
                ->on('advertisementCategory')
                ->onDelete('cascade');
        });

这是我在尝试从请求中插入时收到的错误：

        $newAdvertisement = new Advertisement();
        $newAdvertisement->name = $request->name;
        $newAdvertisement->description = $request->description;
        $newAdvertisement->sellingType = $request->sellingType;
        $newAdvertisement->advertisementType = $request->advertisementType;
        $newAdvertisement->sellingPrice = $request->sellingPrice;
        $newAdvertisement->createdAt = date('Y-m-d H:i:s');
        $newAdvertisement->images = $allImages;
        $newAdvertisement->unlockedAt = null;
        $newAdvertisement->advertisementCategories()->attach($request->selectedCategory);
        $newAdvertisement->save();

SQLSTATE[23000]: Integrity constraint violation: 1048 Column 'advertisementCategory_id' cannot be null (SQL: insert into `advertisement2advCategory` (`advertisementCategory_id`, `advertisement_id`) values (?, 7)) 

Answer 1

您的问题只是操作顺序。 您正在尝试保存多对多房地产的记录，而 $newAdvertisement 尚未保存，因此它没有自己的 ID（这就是您收到错误 Column 'advertisementCategory_id' cannot be null 的原因）。

先保存$newAdvertisement，然后再添加关系。

$newAdvertisement->save();
$newAdvertisement->advertisementCategories()->attach($request->selectedCategory);